Brett Okamoto of ESPN first reported the bout, while also reporting the stakes for the fight have not been determined.
Reyes (12-1-0) has not competed since suffering a controversial loss to UFC light heavyweight champion Jon Jones at UFC 247. Reyes had won 12 straight fights before the loss. Six of those victories came under the UFC banner. Reyes has picked up seven wins as a professional MMA fighter by KO/TKO.
Blachowicz (26-8-0) enters the contest riding a three-fight winning streak, defeating the trio of Luke Rockhold, Ronaldo Souza and Corey Anderson. Blachowicz has not been defeated in almost two years. That defeat came against Thiago Santos in the main event of UFC Fight Night Prague.
UFC 253 takes place on Saturday, September 26 from a to-be-determined location. Israel Adesanya vs. Paulo Costa will headline the card. Fightful is providing live coverage of the event, which streams live on ESPN+ pay-per-view.